This proposal is a renewal request for 25 service units that will allow us to continue the interplay of physiological experimentation and computer simulation that we've pursued since 1989. Over the past year our efforts at modeling cerebral cortical networks engaged in somatosensory information processing have proven useful in guiding our choice of experiments. We currently are writing a series of three articles concerning the effects on cortical neurons of microiontophoretic application of inhibitory receptor agonists and antagonists, and computer simulations thereof. The first paper deals with cortical layer IV results obtained with the inhibitory neurotransmitter GABA, and bicuculline methiodide, a GABA-(g[a]) receptor subtype antagonist. The second paper deals with a comparison of bicuculline results between layer IV and the layers above and below it, and the third deals with data obtained using the GABA-(g(b)) receptor antagonist, baclofen. Future experiments, and simulations thereof, will include microiontophoretic studies using the excitatory neurotransmitter glutamate, as well as ones proposed in our 1992 request that haven't yet been performed.